Electrochemistry: Principles, Methods, And Applications 0198553889, 9780198553885

Table of contents :
Notation and Units xxi
Main Symbols xxii
Subscripts xxvi
Abbreviations xxvii
Fundamental physical constants xxix
Mathematical constants xxix
Useful relations at 25°C (298.15 K) involving fundamental constants xxix
1 INTRODUCTION 1
1.1 The scope of electrochemistry 1
1.2 The nature of electrode reactions 1
1.3 Thermodynamics and kinetics 2
1.4 Methods for studying electrode reactions 5
1.5 Applications of electrochemistry 5
1.6 Structure of the book 6
1.7 Electrochemical literature 7
PART I Principles
2 ELECTROCHEMICAL CELLS: THERMODYNAMIC PROPERTIES AND ELECTRODE POTENTIALS 13
2.1 Introduction 13
2.2 The cell potential of an electrochemical cell 14
2.3 Calculation of cell potential: activities or concentrations? 16
2.4 Calculation of cell potential: electrochemical potential. 18
2.5 Galvanic and electrolytic cells 20
2.6 Electrode classification 21
2.7 Reference electrodes 22
2.8 Movement of ions in solution: diffusion and migration . 25
2.9 Conductivity and mobility 26
2.10 Liquid junction potentials 32
2.11 Liquid junction potentials, ion-selective electrodes, and biomembranes 33
2.12 Electrode potentials and oxidation state diagrams. 34
References 38
xii Contents
3 THE INTERFACIAL REGION 39
3.1 Introduction 39
3.2 The electrolyte double layer: surface tension, charge density, and capacity 39
3.3 Double layer models 44
the first models: Helmholtz, Gouy-Chapman, Stern,and Grahame 45
Bockris, Devanathan, and Muller model 51
chemical models 52
3.4 Specific adsorption 54
3.5 The solid metallic electrode: some remarks 56
3.6 The semiconductor electrode: the space-charge region . 58
3.7 Electrokinetic phenomena and colloids: the zeta potential 64
electrophoresis 66
sedimentation potential 67
electroosmosis 67
streaming potential 68
limitations in the calculation of the zeta potential 68
References 68
4 FUNDAMENTALS OF KINETICS AND MECHANISM OF ELECTRODE REACTIONS 70
4.1 Introduction 70
4.2 The mechanism of electron transfer at an electrode 70
4.3 The mechanism of electron transfer in homogeneous solution 71
4.4 An expression for the rate of electrode reactions 72
4.5 The relation between current and reaction rate: the exchange current 76
4.6 Microscopic interpretation of electron transfer 77
References 81
5 MASS TRANSPORT 82
5.1 Introduction 82
5.2 Diffusion control 83
5.3 Diffusion-limited current: planar and spherical electrodes 85
5.4 Constant current: planar electrodes 90
5.5 Microelectrodes 92
5.6 Diffusion layer 94
Contents xiii
5.7 Convection and diffusion: hydrodynamicsystems 95
5.8 Hydrodynamicsystems: some useful parameters 97
5.9 An example of a convective-diffusion system: the rotating disk electrode
References 102
KINETICS AND TRANSPORT INELECTRODE REACTIONS 103
6.1 Introduction 103
6.2 The global electrode process: kinetics and transport 103
6.3 Reversible reactions 106
6.4 Irreversible reactions 109
6.5 The general case Ill
6.6 The Tafel law 113
6.7 The Tafel law corrected for transport 115
6.8 Kinetic treatment based on exchange current 115
6.9 The effect of the electrolyte double layer on electrode kinetics 116
6.10 Electrode processes involving multiple electron transfer 119
6.11 Electrode processes involving coupled homogeneous reactions 122
References 126
PART II Methods
ELECTROCHEMICAL EXPERIMENTS 129
7.1 Introduction 129
7.2 Electrode materials for voltammetry 129
metals 130
carbon 130
other solid materials 133
mercury 133
7.3 The working electrode: preparation and cleaning 134
7.4 The cell: measurements at equilibrium 136
7.5 The cell: measurements away from equilibrium 137
electrodes 137
supporting electrolyte 138
removal of oxygen 140
7.6 Calibration of electrodes and cells 142
7.7 Instrumentation: general 142
xiv Contents
7.8 Analogue instrumentation 143
potentiostat 146
galvanostat 147
compensation of cell solution resistance 148
7.9 Digital instrumentation 148
References 149
8 HYDRODYNAMIC ELECTRODES 151
8.1 Introduction 151
8.2 Limiting currents at hydrodynamic electrodes 155
8.3 A special electrode: the dropping mercury electrode 157
8.4 Hydrodynamic electrodes in the study of electrode processes 163
reversible reaction 163
the general case 164
8.5 Double hydrodynamic electrodes 165
8.6 Multiple electron transfer: the use of the RRDE 167
consecutive reactions 168
parallel reactions 168
consecutive and parallel reactions 169
8.7 Hydrodynamic electrodes in the investigation of coupled
homogeneous reactions 169
8.8 Hydrodynamic electrodes and non-stationary techniques 171
References 172
9 CYCLIC VOLTAMMETRY AND LINEAR
SWEEP TECHNIQUES 174
9.1 Introduction 174
9.2 Experimental basis 175
9.3 Cyclic voltammetry at planar electrodes 176
reversible system 177
irreversible system 181
quasi-reversible system 183
adsorbed species 185
9.4 Spherical electrodes 187
9.5 Microelectrodes 188
9.6 Systems containing more than one component 188
9.7 Systems involving coupled homogeneous reactions 189
9.8 Convolution linear sweep voltammetry 191
9.9 Linear potential sweep with hydrodynamic electrodes 193
9.10 Linear potential sweep in thin-layer cells 194
References 197
Contents xv
10 STEP AND PULSE TECHNIQUES 199
10.1 Introduction 199
10.2 Potential step: chronoamperometry 200
reversible system 202
quasi-reversible and irreversible systems 203
more complex mechanisms 205
10.3 Double potential step 205
10.4 Chronocoulometry 206
10.5 Current step: chronopotentiometry 208
reversible system 209
quasi-reversible and irreversible systems 211
10.6 Double current step 212
10.7 Methods using derivatives of chronopotentiograms 213
10.8 Coulostatic pulses 214
10.9 Pulse voltammetry 214
tast polarography 215
normal pulse voltammetry (NPV) 216
differential pulse voltammetry (DPV) 217
square wave voltammetry (SWV) 219
other pulse techniques 221
applications of pulse techniques 222
References 222
11 IMPEDANCE METHODS 224
11.1 Introduction 224
11.2 Detection and measurement of impedance 225
a.c. bridges 225
phase-sensitive detectors and transfer function
analysers 227
direct methods 228
11.3 Equivalent circuit of an electrochemical cell 229
11.4 The faradaic impedance for a simple electrode process 230
11.5 The faradaic impedance, Zf, and the total impedance: how to calculate Zf from experimental measurements 232
11.6 Impedance plots in the complex plane 233
11.7 Admittance and its use 236
11.8 A.c. voltammetry 238
11.9 Second-order effects 240
higher harmonics 240
other second-order methods 241
faradaic rectification 242
demodulation 242
xvi Contents
11.10 More complex systems, porous electrodes, and fractals 244
11.11 Нуdrodynamic electrodes and impedance 248
11.12 Transforms and impedance 249
References 251
12 NON-ELECTROCHEMICAL PROBES OF ELECTRODES AND ELECTRODE PROCESSES 253
12.1 Introduction 253
12.2 In situ spectroscopic techniques 254
transmission 254
reflectance, electroreflectance and ellipsometry 255
internal reflection 258
Raman spectroscopy 259
electron spin resonance (ESR) spectroscopy 260
X-ray absorption spectroscopy 261
second harmonic generation (SHG) 263
12.3 Ex situ spectroscopic techniques 263
photoelectron spectroscopy (XPS) 263
Auger electron spectroscopy (AES) 264
electron energy loss spectroscopy (EELS) 266
electrochemical mass spectrometry (ECMS)
and secondary ion mass spectrometry (SIMS) 266
low-energy and reflection high-energy electron
diffraction (LEED and RHEED) 267
12.4 In situ microscopic techniques 268
scanning tunnelling microscopy (STM) 269
atomic force microscopy (AFM) 270
scanning electrochemical microscopy (SECM) 272
scanning ion conductance microscopy (SICM) 273
12.5 Ex situ microscopic techniques: electron microscopy 273
12.6 Other in situ techniques 276
measurement of mass change: the quartz crystal
microbalance (QCM) 276
measurement of absorbed radiation: thermal changes 277
12.7 Photoelectrochemistry 278
12.8 Electrochemiluminescence 282
References 282
PART III Applications
13 POTENTIOMETRIC SENSORS 289
13.1 Introduction 289
Contents xvii
13.2 Potentiometric titrations 290
13.3 Functioning of ion-selective electrodes 294
13.4 Glass electrodes and pH sensors 295
13.5 Electrodes with solid state membranes 297
13.6 Ion-exchange membrane and neutral carrier membrane electrodes 301
13.7 Sensors selective to dissolved gases 303
13.8 Enzyme-selective electrodes 303
13.9 Some practical aspects 304
13.10 Recent developments: miniaturization 305
ISFETs 305
coated wire electrodes 306
hybrid sensors 307
13.11 Potentiometric sensors in flow systems 307
13.12 Electroanalysis with potentiometric sensors 308
References 309
14 AMPEROMETRIC AND VOLTAMMETRIC
SENSORS 310
14.1 Introduction 310
14.2 Amperometric titrations 311
simple amperometric titrations 311
biamperometric titrations 312
amperometric titrations with double hydrodynamic
electrodes 313
14.3 Membrane and membrane-covered electrodes 314
14.4 Modified electrodes .316
14.5 Increase of sensitivity: pre-concentration techniques 318
14.6 Amperometric and voltammetric electroanalysis 322
References 324
15 ELECTROCHEMISTRY IN INDUSTRY 326
15.1 Introduction 326
15.2 Electrolysis: fundamental considerations 327
15.3 Electrochemical reactors 328
15.4 Porous and packed-bed electrodes 331
15.5 Examples of industrial electrolysis and electrosynthesis 332
the chlor-alkali industry 332
metal extraction: aluminium 336
water electrolysis 338
organic electrosynthesis: the Monsanto process 339
15.6 Electrodeposition and metal finishing 341
15.7 Metal processing 345
xvjjj Contents
15.8 Batteries 346
15.9 Fuel cells 349
15.10 Electrochemistry in water and effluent treatment 350
References 351
16 CORROSION 353
16.1 Introduction 353
16.2 Fundamentals 353
thermodynamic aspects 354
kinetic aspects 354
16.3 Types of metallic corrosion 361
16.4 Electrochemical methods of avoiding corrosion 363
electrochemically produced protective barriers 364
sacrificial anodes 364
methods of impressed current/potential 365
corrosion inhibitors 365
References 366
17 BIOELECTROCHEMISTRY 367
17.1 Introduction 367
17.2 The electrochemical interface between biomolecules: cellular membranes, transmembrane potentials, bilayer lipid membranes, electroporation 368
17.3 Nerve impulse and cardiovascular electrochemistry 373
the nerve impulse 374
cardiovascular problems 376
17.4 Oxidative phosphorylation 378
17.5 Bioenergetics 379
17.6 Bioelectrocatalysis 381
17.7 Bioelectroanalysis 387
17.8 Future perspectives 391
References 391
Appendices
Al USEFUL MATHEMATICAL RELATIONS . . 395
Al.l The Laplace transform 395
introduction 395
the transform 395
important properties 397
A1.2 The Fourier transform 398
Contents xix
A1.3 Other useful functions and mathematical expressions 399
the Airy function 399
the gamma function 399
the error function 400
Taylor and Maclaurin series 401
hyperbolic functions 403
Reference 404
A2 PRINCIPLES OF A.C. CIRCUITS 405
A2.1 Introduction 405
A2.2 Resistance 406
A2.3 Capacitance 406
A2.4 Representation in the complex plane 406
A2.5 Resistance and capacitance in series 407
A2.6 Resistance and capacitance in parallel 408
A2.7 Impedances in series and in parallel 410
A2.8 Admittance 410
A2.9 The Kramers-Kronig relations 410
References 411
A3 DIGITAL SIMULATION 412
A3.1 Introduction 412
A3.2 Simulation models 412
A3.3 Implicit methods 414
References 414
A4 STANDARD ELECTRODE POTENTIALS . . 416
INDEX 419